1. Technical Field of the Invention
The present invention relates in general to network diagnostic tools, and in particular, to diagnostic tools for mobile backhaul networks.
2. Description of Related Art
The wireless infrastructure market is migrating towards 3G, replacing traditional Base Transceiver Station (BTS) and Base Station Controller (BSC) elements with University Mobile Telecommunications System (UMTS) Node B and Radio Network Controller (RNC) network elements. With the migration towards 3G underway, the T1/E1 links traditionally connecting the BTS to the BSC are also being replaced with packet switched mobile backhaul networks that provide connectivity between the Node B and the RNC. To deliver traditional T1/E1 voice and data service across the new Internet Protocol (IP)-based mobile backhaul networks, pseudowires are often used. A pseudowire is an emulation of a native service, such as T1/E1, over a packet switched network (PSN), such as an IP-based Multi Protocol Label Switching (MPLS) network. Pseudowires emulate the operation of carrying the native service by segmenting, adapting and encapsulating the T1/E1 traffic into packets of the format required by the PSN.
The term “pseudowire” (PW) typically refers to a PSN tunnel that both originates and terminates on the same PSN. Thus, a PW passes through a maximum of one PSN tunnel between the originating and terminating Provider Edge (PE) routers. To extend the pseudowire service through multiple PSN tunnels (or multiple network segments), multi-segment pseudowires (MSPW) are used. A MSPW is a static or dynamically configured set of two or more contiguous PW segments that behave and function as a single point-to-point PW. Thus, a MSPW can be considered a single PW that is segmented into a number of concatenated hops.
In single-segment pseudowire (SSPW) applications, protection for the PW is provided by the PSN layer. This may be, for example, an RSVP LSP (Resource Reservation Protocol Label Switched Path tunnel) with an FRR (Fast Re-Route) backup and/or an end-to-end backup LSP within an MPLS network. However, in multi-segment pseudowire applications, protection for the MSPW is typically provided by using a primary MSPW and one or more secondary MSPWs on standby in order to provide redundancy.
One of the problems associated with redundant MSPW's is the inability of mobile backhaul network operators to confirm whether or not customer demands for high availability are being met. Availability refers to the percentage of time over a year that a link (here the redundant MSPWs) will be operational. High availability typically requires what is called “five nines,” which means that the link is operational 99.999% of the time (corresponding to being down less than 5 minutes per year). Network operators must ensure that their network links are able to provide high availability to customers who require it. Normally, network operators are able to monitor their links for failures to determine whether they are meeting the high availability demands of customers.
However, with redundant MSPWs, failures may not always be easily ascertained. For example, if the secondary (standby) MSPW fails, the failure is typically not discovered until the primary MSPW fails and an attempt to switch over to the secondary MSPW is unsuccessful. During the time that the secondary MSPW is down, the availability of the end-to-end connection is reduced, and therefore, may be below the customer's required availability level. There is currently no diagnostic mechanism in place to monitor the availability of the secondary MSPW.
In addition, there is currently no diagnostic tool that can effectively determine the potential causes of a connection with a degraded availability value. For example, instances of single points of failure (SPoF) in the backhaul network can reduce the availability of the redundant end-to-end connection. A SPoF may occur where there is a single link to a Provider Edge (PE) node or when an incremental introduction of an additional link to a cell site for dual homing is not property configured for redundant MSPWs. Such SPoF's create lower availability values for the end-to-end connection, and as such, are important to discover.
Another problem associated with multi-segment pseudowires is the lack of diagnostic mechanisms to identify misconfigurations in class of service (CoS) mappings at switching PE nodes in mobile backhaul networks. Switching PE nodes (S-PEs) are intermediate nodes along the MSPW that stitch together different segments of the MSPW. Since each segment may utilize a different PSN tunneling technology, and the supported CoS levels may differ between different PSN tunneling technologies, the S-PEs must be configured to map the CoS level from one tunneling technology to another tunneling technology. A misconfiguration in the CoS mapping can lead to either under-serving or over-serving cell sites.
An additional problem associated with MSPW's is the lack of diagnostic tools to identify misconfigurations in various clock protocols. For example, clock synchronization protocols used in mobile backhaul networks typically have a set of parameters that can be manually modified. In particular, in the IEEE 1588v2 clock synchronization protocol, the modifiable parameters include the “clock_stratum,” “clock_identifier” and “preferred_sync_interval” parameters. If one or more of these parameters is modified to an incorrect value, problems can occur in the clock distribution network. As another example, clock distribution protocols used in mobile backhaul networks typically run master clock selection algorithms to divide the network into clock distribution segments and then create a hierarchy by selecting the master and slave clocks for each segment. This segmenting and hierarchy setting in each segment can be manipulated manually, making the clock distribution protocol vulnerable to errors.